Studies will be carried out on the interactions between the plasma protein fibronectin, other plasma proteins, and the material surface of wettable plastic substrata in order to (1) characterize the adsorption properties of fibronectin and (2) determine what molecular properties of fibronectin determine its adsorptivity. Studies are planned to determine how prior, simultaneous, or subsequent treatment of substrata with fibronectin-depleted plasma influences the interation of fibronectin with the substrata and to ascertain to what extent these interactions are modified under conditions of clot formation or if sulfhydryl bonds are reduced. In addition, the proteolytic sensitivity of fibronectin adsorbed under these conditions will be ascertained. finally, fibronectin sulfhydryl or carboxyl groups will be modified and in other experiments fibronectin will be fragmented by the cyanogen bromide method and the modified proteins and protein fragments will be studied to determine how these molecular changes alter adsorptive properties.